Further Workplace Health and Safety bosses will be grilled at the inquest into the Dreamworld disaster today, after a leading inspector admitted he had "no confidence" in the emergency procedures in place on the Thunder River Rapids ride.

Apple shows off most expensive iPhone yet

Apple has introduced its largest-ever iPhone and a watch that detects heart problems in an attempt to get customers to upgrade to more expensive devices in the face of stagnant global demand for smartphones.

The relatively small changes to its lineup, following last year's overhauled iPhone X, were widely expected by investors and the company's shares ended down 1.2 per cent at $US221.07 on Wednesday.

The strategy has been successful, helping Apple's stock to rise more than 30 per cent this year and making it the first publicly traded US company to hit a market value of more than $US1 trillion.

Apple's new iPhone XS, pronounced "ten S," has a 14.7cm screen, and will be sold at a starting price of $US999 ($A1391). The XS Max, the largest iPhone to date and one of the biggest on the market, has a 16.5cm screen, and will start selling at $US1,099.

"They have finally added a larger-screen phone so that they can directly compete with the Galaxy Note9 products," Gartner analyst Annette Zimmermann said at the event at Apple's Silicon Valley headquarters.

"The larger screen will be very important in China to turn around the trend there, because they have lost some share in the last few years, partly because of screen size," she added.

Apple also introduced a lower-cost 15.5cm iPhone XR made of aluminium, at a starting price at $US749.

The iPhone XS Max's display size is 26 per cent larger than the previous largest iPhone display, marking it the largest increase in screen size since 2014, wrote analyst Gene Munster of Loup Ventures in a note.

This year's three top phones are all more expensive than last year's models.

With two of them starting at $US999 or higher in the United States, Apple appears to be taking advantage of a strong US economy, low unemployment, and rising household wealth.

Looking for ways to lessen reliance on phones, which represent more than 60 per cent its revenue, Apple opened its event by announcing the new Apple Watch Series 4 with edge-to-edge displays, like its latest phones, and they are more than 30 per cent bigger than displays on current models.

It is positioning the new watch as a more comprehensive health device, able to take an electrocardiogram to detect an irregular heartbeat and start an emergency call automatically if it detects a user falling down, potentially appealing to older customers.

The US Food and Drug Administration said it worked with Apple to develop apps for the Apple Watch.

As many as 6.1 million Americans have atrial fibrillation, a heart disease involving irregular heart rhythm for which the Watch could offer an early warning.

"This does have a lot of potential for patients," said Dr Michael Valentine, president of the American College of Cardiology.

"Clinicians face patients every day with palpitations, rapid heart rates, and other symptoms," and the doctors want a more portable monitoring and recording system.